The purpose of this work is to define biochemically the sequence of events involved in the synthesis, modification, transport and final incorporation of viral membrane proteins. A partial characterization of the normal biosynthesis of the glycoproteins of Sindbis virus has been made and will be continued. This normal pattern will now be compared with the situation seen during abortive infection. Two types of abortive infection will be studied: infection with temperature-sensitive mutants, and infection with wild-type virus in the presence of inhibitory doses of glucosamine and 2-deoxyglucose. The viral proteins that accumulate under these conditions will be characterized as to size, degree of modification and intracellular location. In parallel, very similar experiments will be carried out in order to study the synthesis and the assembly of the membrane proteins of the avian tumor viruses. Due to the nature of this infection, viral proteins will be identified using immune precipitation. BIBLIOGRAPHIC REFERENCES: Keegstra, K., Sefton, B. and Burke, D. (1975) Sindbis virus glycoproteins: effect of the host cell on the oligosaccharides. J. Virol. 16:613-620. Sefton, B.M. (1976) Virus-dependent glycosylation. J. Virol. 17:85-93.